1. Field of the Invention
The present invention relates to a toner kit in which a toner used in an image forming process, such as electrophotography, is held in a container. The toner kit of the present invention enables rapid discharge of the toner from the container, and also reduces the quantity of a toner that may remain in the container. Hence, the toner can be rapidly fed to an image forming apparatus, such as a copying machine, and also toner loss can be decreased.
2. Related Background Art
Toners used in electrophotography and containers for holding the toners have been often developed and studied in respectively separate researchers. For this reason, research sections for developing toners have so far devoted their efforts to improving various toner characteristics in electrophotography, but they have not focused on pursing its stability in and dischargeability; from, a toner container.
On the other hand, research sections in charge of toner containers have paid much attention to readiness in handling the containers in physical distribution, cost reduction, and designing.
For example, a toner container manufactured by taking into account only charging quantity of a toner can received therein by 90% or more of the toner with respect to its inner volume. Since, it is difficult to make the container hold a toner in a quantity of 100% of its inner volume, there remains a small unfilled space in the container. Because of this space, the toner can move in the container, but tends to agglomerate or gather to one side during storage or in the course of transportation. This tendency is remarkable in a toner with a poor flowability. In order to prevent the toner from agglomeration or other undesirable phenomena, it is required to shake a container several times when used. However, even when a container has been shaken, blocking tends to occur in the vicinity of an opening of the container. Even with use of a container with increased flatness in its inner wall so as to secure smooth discharge of the toners, the desired results can not be expected.
In another example, for the purpose only of lowering the cost for packaging without taking into account the toner characteristics, a toner is filled in an amount as large as possible for the volume of a container and an opening of the container is made as small as possible. However, an attempt to make the opening smaller tends to cause an undesirable result that the toner remains in the container in a greater proportion. In order to eliminate these problems, one may contemplate that the flowability of a toner is increased so that the discharge performance of the toner can be improved. On the contrary, when the flowability of a toner is increased, a negative result sometimes occurs such that the charge characteristics of the toner is lowered or the scattering of the toner particles within a copying machine becomes remarkably increased.
Reproductions obtained by electrophotography are required to have a high resolution, have no blurred or thickened character image or fine-line image of documents or drawings, have a high density, have a good gradation at solid areas, and are free from image stain (so-called fog) in the white areas.
Under such circumstances, it has been studied in recent years to make the average particle diameter of a toner smaller for the purpose of improving the resolution. In usual instances, the finer the average particle diameter of a toner is made, the lower the flowability of a toner becomes. This tends to result in an inhibition of rapid triboelectric charging between a toner and a carrier, cause fog or spots around image, and brings about a lowering of transfer rate or cleaning properties.
When a copy is taken with an electrophotographic copying apparatus, using a toner having a small particle diameter, a good toner image with a high resolution can be obtained at the initial stage, but an edge effect that brings about an emphasized outline of a toner image may occur after copying on several ten thousand sheets of paper, tending to lower gradation, sharpness, and solid-area uniformity. Particularly under conditions of a high humidity, toner images tend to provide a poor toner image with conspicuous fog and spots around the images. Moreover, it is not preferable that the inside of a machine is contaminated because of the scattering of a toner insufficiently charged. In particular, the above phenomenon is remarkable in the full-color copying that requires a large toner consumption.
This occurs because the toner has such poor flowability that no rapid triboelectric charging takes place between a fed toner and a carrier contained in a developer, so that a toner with insufficient triboelectric charges or a toner with non-uniform charges is brought about and these toners participate in development.
The poorness in flowability of a toner may cause agglomeration of a fed toner in a feed hopper or feed pipe. This not only may obstruct smooth transport of the toner and smooth feed of the toner, but also raises the possibility that a conveyor screw in the feed pipe may be broken because of the blocking of the toner.
As methods used for the purpose of eliminating such difficulties caused by toners, there is a method in which fine particles of an oxide such as silicon oxide, titanium oxide or aluminum oxide are mixed in a toner as a flowability improver. When any of these oxides is mixed in a toner, the flowability of the toner is certainly improved, compared with an instance in which none of them is added. If, however, the oxide is merely mixed in a toner, the flowability of the toner can not be sufficiently improved, sometimes causing the difficulties as stated above.
This occurs presumably because the flowability improver is not uniformly imparted to particle surfaces of the toner.
When the toner to which no flowability improver is not uniformly imparted is used, the toner and the flowability improver gradually form a filmy thin coating because of an external force produced by a means such as a cleaning blade, bringing about a filming phenomenon.
If the flowability improver is insufficiently dispersed, the flowability improver is not uniformly strongly adhered to toner particle surfaces, so that liberated flowability improver or an agglomerate of the flowability improver is electrostatically adhered to the surface of a photosensitive member. As a result, a film is formed on the photosensitive member by an external force to affect the development.